The invention relates to a device for forming a groove on a single-page or multi-page sheet or on a web of paper, plastic or metal, passing through an annular gap between two circular scoring elements that rotate in opposite directions around parallel axes, wherein one scoring element is embodied as a scoring knife that is tapered toward the edge region in the manner of a ridge and the opposite-arranged scoring element is embodied as a score anvil.
Devices of this type are disclosed, for example, in the European patent document EP 0 627 303 A1, WIPO patent document WO 2004/073966 A1 and European patent document EP 1 845 046 A1.
The European patent document EP 0 627 303 A1 discloses a rotary embossing machine that is provided for the continuous scoring of carton blanks with two counter-rotating cylinders, between which a carton blank is clamped in and conveyed. One of the cylinders is provided along the periphery with an outward projecting embossing profile, which reduces the cross section with increasing diameter during one or a plurality of phases. The second cylinder contains a circular groove that is positioned opposite the embossing profile of the first cylinder. The aforementioned embossing device is suitable for use with thicker products, but not with thin products such as covers for magazines or other types of printed products.
The WIPO patent document WO 2004/073966 A1 discloses a system, which can be used to score and perforate flat materials by affixing strips to a drum rotating around a first axis. The strips that project from the cylindrical surface of the drum engage in a wheel that rotates around a second axis and is provided with one or a plurality of grooves. The first and the second axis in this case are arranged parallel to each other. The material, composition and geometry of the one or a plurality of strips that can be attached to be detachable to the drum can differ. If the strips are made of plastic, as described, they are subject to heavy wear and tear and must be replaced regularly with new ones. To obtain an optimum groove or perforation in the flat materials to be processed, the strips must be attached to the drum circumference with extreme precision in an axial, as well as radial, direction, an operation that can be very time-consuming and involved.
Differences in the quality and types of materials, such as non-printed or printed sheets, signatures, or foils also result in different types of behavior during the processing. Thus, it is known that sensitive sheets have a tendency to tear or break when they are folded along deformations caused by scoring, in particular if individual printed sheets are used as casings for books, softcovers or the like. The scoring displaces and/or compresses the material, thus providing the materials or sheets that are scored with a bending location that functions as a hinge. If the contact pressure applied with the scoring knife is too high, the sheets or the web are cut either partially or completely. If the contact pressure is too low, the fold may deviate from the intended bending location after the scoring. Scoring devices are also known where the bulge generated by the scoring knife, also called a scoring bulge, following the folding operation comes to rest either on the outside (positive scoring) or on the inside (negative scoring) between the legs of the folded sheet. To be able to process the broadest possible spectrum of sheets, scoring devices are known which can be fitted or retrofitted for the positive and negative scoring.